Siemens SIPROTEC 7SJ62 User Manual

Functions
2.2 Overcurrent Protection 50, 51, 50N, 51N
SIPROTEC, 7SJ62/64, Manual
C53000-G1140-C207-2, Release date 01.2008
83
Measurement Methods
The comparison values to be used for the respective element can be set in the setting sheets for the elements.
• Measurement of the fundamental harmonic (standard method):
This measurement method processes the sampled values of the current and filters in numerical order the
fundamental harmonic so that the higher harmonics or transient peak currents remain largely unconsidered.
• Measurement of the true r.m.s. value
The current amplitude is derived from the sampled values in accordance with the definition equation of the
true r.m.s. value. This measurement method should be selected when higher harmonics are to be consid-
ered by the function (e.g. in capacitor banks).
• Measurement with instantaneous values
This method compares the instantaneous values to the set threshold. It does not perform a mean-value cal-
culation and is thus sensitive with regard to disturbances. This measurement method should only be select-
ed if an especially short pickup time of the element is required. With this measurement method, the operating
time of the element is reduced compared to the measurement of true r.m.s. values or fundamental harmonics
(see „Technical Data“).
The type of the comparison values can be set under the following addresses:
50-3 element Address 1219 50-3 measurem.
50-2 element Address 1220 50-2 measurem.
50-1 element Address 1221 50-1 measurem.
51 element Address 1222 51 measurem.
50N-3 element Address 1319 50N-3 measurem.
50N-2 element Address 1320 50N-2 measurem.
50N-1 element Address 1321 50N-1 measurem.
51N element Address 1322 51N measurem.
High-set Current Elements 50-2, 50-3 (phases)
The pickup currents of the high-set elements 50-2 PICKUP or 50-3 PICKUP can be set either at address
1202 or 1217. The corresponding delay time 50-2 DELAY or 50-3 DELAY can be configured under address
1203 or 1218. It is usually used for purposes of current grading intended for large impedances that are prev-
alent in transformers or generators. It is specified in such manner that it picks up faults up to this impedance.
Example of the high-set current element
50-2 PICKUP: Transformer used for busbar supply with the following
data:
Based on the data above, the following fault currents are calculated:
Rated power of the transformer S
NomT
= 16 MVA
Transformer impedance ZTX = 10 %
Primary nominal voltage V
Nom1
= 110 kV
Secondary nominal voltage V
Nom2
= 20 kV
Vector groups Dy 5
Starpoint Grounded
Fault power on 110 kV–side 1 GVA
3-Phase High Voltage Side Fault Current I"
k3, 1, 110
= 5250 A
3-Phase Low Voltage Side Fault Current I"
k3, 2, 20
= 3928 A
On the High Voltage Side Flowing I"
k3, 2, 110
= 714 A
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Siemens SIPROTEC 7SJ62 Specifications

General

Brand	Siemens
Model	SIPROTEC 7SJ62
Category	Relays
Language	English